I am about at my wits end... the basics 1993 D250 12v cummins 5 speed. Symptoms... Started with the Hvac and windows not working. I could bridge across and get them to work fine. Never found any breaks or shorts. Then the cruise control started acting funny, would cut in and out going down road some days would not work at all then stopped working all together. Finally a buddy borrowed it to pull a 5th wheel trailer as he pulled into its parking spot it died. I have checked the fusible links all good except the one that feeds the solid red i dont believe its the link as there is no power before or after the link.... When you turn ignition NOTHING happens no dash lights, buzzing, warning light's etc when you turn to start zilch happens as well. Been doing a lot of reading and I am thinking its either the ignitin switch itself, a bad relay or possibly a bad ecu?? How can i go through a process of elimination before i just start replacing parts! Thank you in advance!!!